3 or 4
Down in my basement,i am going to get one out the next time it get's warm,and put it on my f75se with the 15dd coil,it's needed with that coil,and i will give it a try,i did try it one time and it was kinda hard to get used to ,but with the 15dd ,i must use one,happy hunting,i will let you know how it turn's out,Earl